It’s a problem unlikely to trouble U.S. politicians any time soon: there’s so much common ground between Britain’s three largest political parties that they struggle to define themselves against their rivals. Yes, their histories and traditional values are quite different. But since Tony Blair led Labour to the center and thence to three successive electoral victories, the Conservatives and Liberal Democrats have been fighting to annexe chunks of the same territory. Indeed, last year Conservatives and Lib Dems shacked up together on a patch of middle ground to govern the U.K. in coalition, leaving Labour as the only mainstream opposition. But what can Labour find to oppose? Straightjacketed by savage economic conditions, it has little real room for maneuver on questions of tax and spend. And with all three parties espousing socially liberal views and helmed by personable, articulate, posh-ish white men in their 40s, the dividing lines can be hard to spot. So when those personable leaders take to the podium at their annual party conferences, they face a tricky job: to persuade their delegates that they’re staying true to party roots while convincing the wider world that they’re not closet ideologues. Oh, and that they can offer something their lookalike, soundalike competitors cannot.

For Ed Miliband, exactly a year into the post of Labour leader after elbowing aside his elder brother who’d been the favorite for the role, one USP is celebrity support. In the early days of the Blair era, actors and rock musicians clamored for invitations to 10 Downing Street and regularly allowed themselves to be filmed, rapt, in the front row at party conferences. After the Iraq war their numbers dropped sharply, but Labour still commands greater star power than the other parties. Miliband’s Sept. 27 keynote conference speech wasn’t attended in person by many famous people, but a range of notables served as celluloid warm-up acts, from Jason Isaacs, better known as Lord Voldemort’s evil servant Lucius Malfoy, to Aung San Suu Kyi. These cameos pleased delegates, but this was nothing to the racing pulses and pulsating excitement surrounding an appearance at Labour’s conference, on the eve of Miliband’s speech, by Hugh Grant.

In Love Actually, the actor was only slightly less convincing as Britain’s Prime Minister than Gordon Brown proved in real life. Now Grant has found a role more suited to his talents, as an activist urging a thorough investigation of hacking and the other dark arts practiced by some segments of his country’s national press until the scandal shuttered News Corporation’s British Sunday tabloid News of the World. To keep the issue at the forefront of the political agenda, Grant agreed to address meetings at all three party conventions. In her pre-recorded address to Labour, Suu Kyi told delegates that in Burma Britain’s party conferences seem a distant dream. To Grant they may feel like a nightmare. He’s endured the Liberal Democrat’s conference in Birmingham and Labour’s shindig in Liverpool and is expected at the Conservatives’ gathering in Manchester, which runs from Oct. 2-5.

The actor aims to lobby politicians, not to endorse any of the parties. But that hasn’t stopped some MPs, giddy after breathing the same air as a bona fide film star, from claiming Grant as a fellow traveler. Miliband resisted that temptation, but in his conference address sought instead to position himself as an ally of Grant and other significant players in the the humbling of Rupert Murdoch—or “Voldemort,” as Grant has dubbed the press baron. Miliband was the first of the party leaders to criticize News Corp’s handling of the hacking affair and to ask hard questions about the company’s bid to acquire an even greater share of the U.K. media. In so doing said Miliband, burnishing his tough-guy credentials, he broke “the number one rule of British politics—don’t mess with Rupert Murdoch.” (According to Westminster lore, Voldemort casts a spell—or at any rate dictates press coverage—that boosts or destroys politicians.)

Miliband’s stance does mark him out from Conservative leader David Cameron, who appointed the former News of the World editor Andy Coulson as his chief spin doctor, hobnobbed with News Corp. executives and refused to repudiate his tarnished friends as the scandal blossomed. No wonder Miliband was tempted into trying to make political capital out of something that not only sets him apart from Cameron, but makes him look better. But the Labour leader’s boast of derring-do—like the rest of his speech—also served to highlight his vulnerabilities. It’s not just, as Grant pointed out, that Miliband’s predecessors had cosied up to News Corp. “[Labour’s] years of association as a party with the Murdoch press—I’m not really sure that suited you. I’m not sure that was your best look,” said the actor. It’s also that in trumpeting his own bravery in speaking out on hacking, Miliband accidentally drew attention to the fact that all he can do and all he has done, since becoming Labour leader, is speak out. Legislation introduced by the coalition government and signed into law on Sept. 15 altered Britain’s electoral cycle to five-year fixed terms. On that basis Miliband won’t have a crack at becoming Prime Minister before May 2015. In the meantime his primary job is to hold the government to account and to prepare for power.

The dawning realization that Labour faces at least a few years in the wilderness sapped the spirits of delegates. (Last year the adrenalin produced by the Miliband v. Miliband leadership contest distracted attention from Labour’s underlying predicament.) Fears that the victorious Miliband may not be the leader capable of delivering Labour from the wilderness deepened the gloom, especially after publication of a Sept. 26 ComRes opinion poll showing Labour falling behind the Tories even though the Tories, backed by their Lib Dem partners, are inflicting painful cuts to British public spending. Miliband’s personal ratings remain discouraging with 24% of respondents to the ComRes poll judging him a “credible Prime Minister-in-waiting” compared to 57% who disagreed. Many of his party colleagues appear to share the misgivings of the wider voting public. “He’s hopeless. It’s hopeless,” volunteered a lifelong Labour activist.

His keynote may have pushed Miliband a little higher in the polls, though it felt curiously detached from real world events, not least in the failure to do more than flick at the euro zone crisis. The speech did contain some good gags, the best of which related to Miliband’s July surgery to correct a deviated septum. “Typical Labour leader. He gets elected and everything moves to the center,” he joked, and joking aside, Miliband’s enunciation seemed clearer, post-op. His delivery was almost prime ministerial. But almost prime ministerial, as Grant proved in Love Actually and Brown demonstrated in real life, may not be enough to win over skeptics.